Spinodal-based co-continuous composites for high performance battery electrodes

ABSTRACT

Electrodes and methods of creating co-continuous composite electrodes based on a highly porous current collector are provided. In one embodiment, a method for creating an electrode includes depositing a thin layer of material on the polymer template, removing polymer material of the polymer template and depositing a second material. The method may also include controlling internal surface area per unit volume and the active material thickness of at least the second material to tune the electrochemical performance of the electrode. In one embodiment, a composite electrode is provided including interpenetrating phases of a metal current collector, electrolytically active phase, and electrolyte.

PRIORITY

This application is a divisional of U.S. application Ser. No. 15/744,046filed on Jan. 11, 2018, now U.S. Pat. No. 10,714,758, titledSPINODAL-BASED CO-CONTINUOUS COMPOSITES FOR HIGH PERFORMANCE BATTERYELECTRODES which claims priority to and is the National Stage filing ofInternational Application No. PCT/US2016/037040, titled SPINODAL-BASEDCO-CONTINUOUS COMPOSITES FOR HIGH PERFORMANCE BATTERY ELECTRODES filedon Jun. 10, 2016, which claims the benefit of U.S. ProvisionalApplication No. 62/175,150 filed on Jun. 12, 2015, titled SPINODAL-BASEDCO-CONTINUOUS COMPOSITES FOR HIGH PERFORMANCE BATTERY ELECTRODES, thecontent of which is expressly incorporated by reference in its entirety.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under Grant No.CMMI1301489, awarded by the National Science Foundation. The governmenthas certain rights in the invention

BACKGROUND

High performance electrochemical storage devices can be divided into twomain categories: batteries and supercapacitors. Batteries traditionallydeliver high energy, but suffer when it comes to power delivery. On theother hand, supercapacitors are noted for having large power densitiesat the sacrifice of delivering sub-par energy. In order to meet futureenergy demands, the gap between batteries and supercapacitors must bebridged by creating devices that concurrently deliver both high energyand power.

FIG. 1 depicts a conventional pore structure. Three-dimensional porouscomposite electrodes are currently used in commercial applications, inparticular for many battery chemistries including Nickel Metal Hydride(NiMH), Lithium Ion and Lead Acid. Most NiMH batteries utilize a nickelfoam cathode to increase electrical conductivity. These nickel foamsgenerally have 80-180 holes per inch, with an average hole diameter of˜0.25 mm A layer of electrolytically active materials is then attachedto the nickel foam in a slurry addition, creating a 3D compositeelectrode. This method was first patented by General Electric Company in1967 with a desirous pore structure that contains about 100 pores perinch or pore sizes of about 250 μm. The Mitsubishi Materials Corporationin 1996 improved upon the initial design through considering pores onthe range of 60 to 700 μm, thus slightly reducing the length that ionsand electrons need to flow. This foam type architecture can be utilizedin a variety of materials including nickel, copper, carbon basedmaterials, and a range of other electron conducting phases.

In order to meet growing energy demands, there have been many attemptsto improve foam morphology, through creating materials that have a moresymmetric pore architecture and through reducing overall poredimensions, enabling low-resistance transport paths for ion andelectrons throughout the structure. These attempts all have drawbacks.FIG. 2 displays various different conventional architectures. Section200 depicts a lithography defined microstructure, section 205 depicts ananofoam architecture, section 210 depicts a nanowire based array, andsection 215 depicts an inverse opal structure. Multi-beam laserlithography has been used to create nanostructures with a face centeredcubic lattice and uniform pore distribution with pore sizes of about˜800 nm. The nanofoam architecture is composed of interconnecting fibersranging from 100-1000 nm in diameter and porosity of 99%. Nanowire basedarchitectures consist of aligned nanowires with uniform diameters thatcan range from ˜1 nm to ˜500 nm, and lengths as long as 1 μm. Theinverse opal structure consists of pores that range from ˜200 nm to ˜10μm depending on the initial spheres used to create the template, andoffers uniform pore distribution.

Prior art methods suffer from major disadvantages. Regarding foams, theelectrolytically active phase is deposited via a slurry addition, whichfills the pores and does not allow for a percolating pathway for theelectrolyte. The processing of foams, in combination with the large poresizes (˜0.25 μm) and pore distribution, creates long pathways for ionsand electrons to transport, limiting the achievable power densities tothat of traditional batteries.

Lithography defined structures have a uniform pore size distribution,but the pore size itself is not uniform. This limits the active materialthat can be deposited while also ensuring a percolating passage for eachphase. Moreover, this method requires expansive techniques such asmulti-beam laser interference lithography and argon plasma sputtering.The processing step also inhibits the thickness of the electrode to ˜4μm, limiting the total energy that can be stored in the device.

Regarding nanofoams, the diameters of the fibers that comprise thestructure range over an order of magnitude producing pores and a poredistribution that are not uniform. Further deposition of an activematerial could then cause a blockage, not allowing the electrolyte tofreely flow within the structure.

Regarding nanowires, due to the small diameter of these nanowires, theyhave a tendency to colligate together, creating non-uniform pores andpore distribution. As with other conventional methods, this can increasethe resistive paths for ions and electrons, which in turn will limit thepower density. Furthermore, the distance between the wires is verysmall, limiting the amount of active material that can be deposited andin turn, the energy density.

Regarding inverse opal structures, similar to lithography definedstructures, the pore structure is non-uniform, limiting the amount ofactive material that can be deposited while still keeping a continuouspath for the electrolyte. Additionally, this processing technique canonly produce electrodes with a thickness of up to ˜15 μm, limiting thetotal amount of stored energy. This method also requires extensivetechniques such as evaporative deposition and electrodeposition.

BRIEF SUMMARY OF THE EMBODIMENTS

Disclosed and claimed herein are methods for creating a compositeelectrode, composite electrodes and batteries including a compositeelectrode. One embodiment is directed to a method for creating acomposite electrode including depositing a layer of metal material on apolymer template to form a metal coated structure, wherein the polymertemplate is a porous structure having a uniform pore structure with adefined internal surface area per unit volume. The method also includesremoving polymer material from the metal coated structure to form ametal shell, wherein the metal shell includes a uniform pore structurewithin the metal shell with an internal surface area per unit volumebased on the polymer template. The method also includes depositing anactive material on the metal shell to form a composite electrode,wherein thickness of the active material in the composite electrode iscontrolled to tune the electrochemical performance of the compositeelectrode.

In one embodiment, the polymer template is a bicontinuous interfaciallyjammed emulsion gel.

In one embodiment, the polymer template includes a uniform pore geometrywith a uniform pore distribution.

In one embodiment, pores of the metal shell are uniform and range fromabout 5 μm to about 450 μm in length.

In one embodiment, removing the polymer includes sintering the metalcoated structure.

In one embodiment, the metal shell is a nickel metal shell.

In one embodiment, the active material is Nickel/Nickel Hydroxide(Ni/Ni(OH)₂).

In one embodiment, the thickness of the active material is about 1 μmthick.

In one embodiment, performance of the composite electrode is based onthe internal surface area per unit volume and thickness of the activematerial.

In one embodiment, electrochemical performance of the compositeelectrode is governed by independent tuning of pore diameter andthickness of the active material.

In one embodiment, the method includes forming the polymer template witha desired pore structure prior to the depositing the layer of metalmaterial on the polymer template.

In one embodiment, the composite electrode is configured as a porouscurrent collector.

In one embodiment, the composite electrode is configured as a cathodefor a nickel metal hydride battery.

In one embodiment, thickness of the composite electrode is within therange of about 15 μm to about 500 μm.

Another embodiment is directed to a battery electrode including acomposite electrode having a porous structure, the composite electrodeformed by a metal structure having a uniform pore structure with adefined internal surface area per unit volume, and an active materialcoating the metal structure, wherein thickness of the active material inthe composite electrode is controlled to tune the electrochemicalperformance of the composite electrode.

In one embodiment, the metal structure is formed by nickel.

In one embodiment, the pore geometry and distribution of the metalstructure is tuned for electrochemical performance of the compositeelectrode.

In one embodiment, the active material coating is Nickel/NickelHydroxide (Ni/Ni(OH)₂).

In one embodiment, thickness of the composite electrode is within therange of about 15 μm to about 500 μm.

Another embodiment is directed to battery including an electrolyte, ananode electrode, and an cathode electrode. The cathode is a compositeelectrode having a porous structure, the composite electrode formed by ametal structure having a uniform pore structure with a defined internalsurface area per unit volume, and an active material coating the metalstructure, wherein thickness of the active material in the compositeelectrode is controlled to tune the electrochemical performance of thecomposite electrode.

Other aspects, features, and techniques will be apparent to one skilledin the relevant art in view of the following detailed description of theembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the present disclosure willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

FIG. 1 depicts a conventional pore structure;

FIG. 2 depicts various different conventional architectures;

FIG. 3 depicts a graphical representation of bijel formation accordingto one or more embodiments;

FIG. 4 depicts a process for creating a polymer template according toone or more embodiments;

FIG. 5 depicts a process for creating a composite electrode according toone or more embodiments;

FIG. 6 depicts a graphical representation of independent tuning ofdomain size and material thickness according to one or more embodiments.

FIG. 7 depicts electrochemical measurements of a composite electrodeaccording to one or more embodiments;

FIG. 8 depicts ragone plots for a composite electrode according to oneor more embodiments;

FIG. 9 depicts a graphical representation of a battery including acomposite electrode according to one or more embodiments; and

FIG. 10 depicts a process for creating a composite electrode accordingto one or more embodiments.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Overview and Terminology

One aspect of the disclosure is directed to processes for creatingcomposite electrodes with desired microstructure characteristics thatgovern electrostatic performance. In one embodiment, a process isprovided that allows for independent tuning of pore diameter and activematerial thickness of the composite electrode. In that fashion, anelectrode is provided that allows for efficient ion transport toelectrochemically active sites throughout the entire electrode. Controlof pore characteristics and active material thickness can beindependently tuned based on one or more or the processes describedherein.

In one embodiment, methods of creating co-continuous compositeelectrodes based on a highly porous current collector are provided. Inone embodiment, a method includes creating an electrode by depositing athin layer of material on the polymer template, removing the polymermaterial of the polymer template and depositing a second material. Themethod also includes controlling internal surface area per unit volumeand the active material thickness of at least the second material totune the electrochemical performance of the electrode. In oneembodiment, the methods provide short pathways for ion and electrontransport, as well as a systematic approach to tune the electrochemicalproperties of the electrode to produce electrochemical storage devicesthat simultaneously delivery high energy power densities. In oneembodiment, the first step is creating a sacrificial bicontinuouspolymer template that exhibits the unique morphological conditions ofthe embodiments. A conductive metal is then deposited onto the polymertemplate and the template is removed creating a composite electrode. Thethickness of the active material can also be varied over a wide range(e.g., ½ of the pore diameter of less). As a result, a highly porouscurrent collector is created from the co-continuous composite electrodesbased on a highly porous current collector.

In one embodiment, a composite electrode is provided. The compositeelectrode may be prepared for inclusion in interpenetrating phases of ametal current collector, electrolytically active phase, and electrolyte.The composite electrode may be a highly porous current collector.

In one embodiment, a microstructural design can be used to createelectrodes for a wide variety of electrochemical applications,especially where large energy and power densities are simultaneouslyrequired. By enhancing the transport kinetics within the microstructurethrough minimizing the travel length of ions and electrons, the overallelectrochemical performance can be enhanced significantly. The synthesistechnique described in the following sections is not limited to anycertain chemistry, thus a wide variety of materials can be used. Throughrestructuring electrode architecture, traditional materials used inbatteries or electrochemical supercapacitors can exhibit an increase involumetric energy and power density, allowing for higher energy andpower output, or miniaturization of these devices. The ability toprovide more energy and power per a given volume is more important whenconsidering the ever-growing energy demands and push towardsminiaturization.

One aspect of the disclosure relates to designing an electrodearchitecture to enable a percolating path for ions and electrons totravel throughout the entire structure, to minimize the length andresistance of transport pathways, and to enable a large volumetricdensity of active materials. In one embodiment, a 3D electrode isprovided that contains interpenetrating phases a metal currentcollector, electrolytically active phase, and electrolyte.

In one embodiment, a uniform pore geometry is provided. In comparison toconventional devices or methods which provided non-uniform pores, auniform pore geometry may be provided by a co-continuous architecture.In one embodiment, the architecture offers pores of a uniform sizethroughout the entire device. This allows for efficient ion transport tothe electrochemically active sites throughout the entire electrode.

Another aspect is directed to independent tuning of microstructuralparameters that govern electrochemical performance. In one embodiment,the processing technique allows for independent tuning of the porediameter and the active material thickness. The two control knobs (e.g.,pore diameter and the active material thickness) mediate the overallelectrochemical behavior of the system. Thus, with the ability to tuneeach of pore diameter and the active material thickness individually,the electrochemical performance can be tuned over wide range, with thepossibility to tune a given performance characteristic.

FIG. 3 depicts a graphical representation of bijel formation accordingto one or more embodiments. According to one embodiment, bijel formationis used to generate a polymer template. Bijel formation as discussedherein can produce a unique morphologies to provide a uniform poregeometry. In one embodiment, a morphology described in this disclosureutilizes a class of soft materials known as bicontinuous interfaciallyjammed emulsion gels (e.g., bijels). The formation of these softmaterials occurs through arrested phase separation of a binary liquidmixture 305 undergoing spinodal decomposition in the presence ofneutrally wetting colloidal particles 310. During phase separation, theparticles 310 absorb to the fluid-fluid interface 311, and the resultingsoft material is comprised of two bicontinuous and interpenetratingfluid domains 315, 320. The subsequent self-similar domains can be tunedover wide range (e.g., ˜5 μm to 405 μm) solely through the volumefraction of particles. Herein lies the first control knob according toone embodiment, through varying characteristic domain size, the internalsurface area per unit volume, here denoted as 6, is consequently varied.These soft materials can be transformed to a polymer template byexploiting the incompatible chemistries of the two fluid domains,through selectively polymerizing one phase, as shown in FIG. 4.

FIG. 4 depicts a process 400 for creating a polymer template (e.g.,scaffold) according to one or more embodiments. In one embodiment, amonomer 410 mixed with a photoinitiator is placed on top of the bijel405 and allowed to equilibrate, shown as 415. Bijel templates are thenformed through photopolymerization. For bijel formation, a variety ofbinary fluid systems that undergo spinodal decomposition andnanoparticles can be used. According to one embodiment, a criticalsolution of water/2,6-luitine and 697 nm fluorescent silicananoparticles were used for bijel formation. The bijel was transformedinto a bicontinuous polymer template through selectively polymerizingthe lutidine phase with a hydrophobic monomer (1,6 hexanedioldiacrylate)mixed with a photoinitiator (Darocur 1173), shown as 420. Silicaparticles 425 are then removed through a quick hydrofluoric acid etchcreating a polymer scaffold 430.

FIG. 5 depicts a process 500 for creating a composite electrodeaccording to one or more embodiments. In one embodiment, FIG. 5 depictssteps to create co-continuous composite 520 according to one or moreembodiments. For proof of concept and according to one embodiment, aNickel/Nickel Hydroxide (Ni/Ni(OH)₂) electrode 520 was synthesized.However, processing techniques can be expanded beyond that ofNickel/Nickel Hydroxide (Ni/Ni(OH)₂) chemistries according to one ormore embodiments, creating a general platform for the synthesis ofelectrochemical composites. In one embodiment, a thin coating of nickelis deposited on the polymer template 505 through electroless plating.According to one embodiment, the polymer template includes a uniformpore geometry and a co-continuous architecture. The plating procedureallows for a uniform 1 μm thick coating of nickel throughout the entirevolume of polymer template 505, and does not require any expensiveequipment, as is the case for electrodeposition. Nickel coated polymertemplate 510 is generated by the electroless plating of polymer template505. In one embodiment, the polymer is removed through sintering in airat 500° C. for 4 hours, and subsequently sintering at 450° C. for 8hours under H₂ (4% in Ar) to ensure reduction of the scaffold to purenickel, such as nickel shell 515. In one embodiment, an active material,such as nickel hydroxide, is then deposited on nickel shell 515 throughchemical bath deposition, and the length of this layer could besystematically controlled through this step. This processing step, likethat of electroless plating procedure, does not require any expensiveequipment and thus, is fairly low cost. This final step also providesthe second control knob since this layer controls the ion transport pathin the active layer of the Nickel/Nickel Hydroxide (Ni/Ni(OH)₂)electrode 520.

According to one embodiment, the ability to independently tune twocontrol knobs (the internal surface area per unit volume and the activematerial thickness (δ)), allows for the ability to tune theelectrochemical performance of an electrode for a certain designrestraint. The effectiveness of the embodiments in regards to tuning theelectrochemical performance is discussed below. Regarding uniform poregeometry and pore distribution, the embodiments offer a uniform poregeometry that also results in a uniform pore distribution. This ensuresthe percolating passages for every phase of the composite electrode, thecurrent collector, the electrochemically active phase, and theelectrolyte. Additionally, due to the uniform pore geometry, this designoffers greater control of the amount of active material that can bedeposited while still insuring connectivity of each phase throughout thevolume.

Regarding short transport lengths for electrons, the embodiments offerone or more advantages. The pore size of the current collector can be anorder of magnitude less than the prior art of the foam architecture.This allows for deposition of a thinner layer of active material whilestill maintaining a large volume fraction of active material. Thus, thepathways for ion and electron transport are decreased, increasing thepower density. Through careful design of pore size and active materialthickness, this design can offer the power density of a supercapacitor,with the energy density of battery, bridging the gap between twotechnologies.

Regarding independent tuning of the morphological parameters that governelectrochemical performance, the embodiments offer processes to allowfor independent tuning of the pore size (which governs the internalsurface area per volume) and the active material thickness. As such, adesign is provided for next-generation electrodes to meet a wide varietyof design constraints, including large energy and power densities.

Regarding cost, the embodiments offer lower cost solutions. Conventionalmethods require processing steps performed by expensive equipment.Embodiments described herein may be executed using an ultra violet lamp,which is relatively inexpensive. Additionally, the maximum temperatureneeded to remove the polymer is 500Y C in certain embodiments, where asa temperature of 1000° C. is needed for lithography defined structures.

Regarding electrode thickness, many of the conventional techniques arelimited to a maximum thickness of ˜15 μm or less due to processingtechniques. The embodiments offer much thicker electrodes ˜500 μm.Limiting electrode thickness also limits the total energy that can bestored in the cell. Thus, in order to create devices with a greateramount of stored energy, the ability to create thick electrodes asoffered by the embodiments is crucial.

FIG. 6 depicts independent tuning of domain size and material thicknessaccording to certain embodiments. In an exemplary embodiment, domainsize and active material thickness were independently tuned for an arrayof electrodes with a domain size 601 of (8 μm<ξ<22 μm) and activematerial thickness (475 nm<δ<1 μm) was fabricated.

FIG. 6 depicts the microstructure of 3D-bicontinuous electrodes 600. Insections 605, 610, 615, a bare nickel shell with 8 mm, 15 mm, and 22 mmdomains are shown respectively. In sections 620, 625, 630 of FIG. 6, the15 mm electrode with three different active material thicknesses of 475nm, 675 nm, and 1 mm are shown respectively. The scale bars denote 25 mmfor sections 605, 610, 615, 10 m for sections 620, 625, 630 and 1 mm forthe insets 621, 626, 631 in sections 620, 625, 630.

To explore the electrochemical characteristics of these electrodes,cyclic voltammetry and charge/discharge tests were performed for eachelectrode. These tests were performed in the three-electrode cell, withAg/AgCl reference electrodes, platinum counter electrode, and 6M KOH aselectrolyte. As a representative example, the results of theelectrochemical tests for the electrode with ξ=22 and δ=675 are shown inFIG. 7. The CV curves show two clear peaks, corresponding to theoxidation and reduction of the active material according to thereversible reaction Ni(OH)₂+OH←→NiOOH+H2O+e⁻. Specific capacitancevalues were then calculated from both the CV curves and the dischargecurves, and a maximum gravimetric capacitance of 2148.5 F/g wasachieved, close to the theoretical value of 2305 F/g. When increasingthe discharge rate to 250 A/g, the specific capacitance decreased byonly 39% (1310 F/g) from its maximum value. This demonstrates efficientuse of the active material even at exceedingly large current densities.This electrode was cycled at a current density of 25 A/g for 1000cycles, and the electrode maintained at least 80% of its original valuethroughout the 1000 cycles, demonstrating the excellent stability of theelectrode.

FIG. 7 depicts electrochemical measurements of the 22/675 Nickel/NickelHydroxide (Ni/Ni(OH)₂) composite electrode. Section 705 of FIG. 7depicts CV curves at various scan rates. Section 710 of FIG. 7 depictsgalvanostatic discharge cures at various current densities. Section 715of FIG. 7 depicts gravimetric capacitance as a function of currentdensity. Section 720 of FIG. 7 depicts capacitance retention as afunction of cycle number. Discharge rates are at 25 A/g for FIG. 7.

To demonstrate how control over pore size and actual material thicknessallows for tuning the electrochemical performance of electrodes,gravimetric and volumetric power and energy densities are plotted in theRagone plots in FIG. 8. The effect of thickness of the electroliticallyactive material can be clearly seen in gravimetric energy and powerdensities. The general shape of these graphs shows a roughly constantenergy density until a critical power density is reached, which is mostlikely the point where ion diffusion though the active layer becomes todominate the electrochemical performance. Thus, the gravimetricperformance can solely be tuned though active material thickness in someembodiments. Additionally, matching or exceeding the best values can beprovided by providing at least 2× the energy density at comparablespecific powers for 3 out of 4 reported values. The volumetric datademonstrates how the electrochemical performance can be tuned thoughboth the active layer thickness and the pore diameter, which controlsthe amount of active material in a given volume. The electrode with thesmallest pores and the thickest layer of active material (the electrodewith the greatest amount of active material in a given volume) exhibitsthe highest volumetric energy density at low power densities. Comparingto conventional values, electrodes according to embodiments herein offer20× the energy at high power densities and 730× power at comparableenergy densities. Notably, conventional values representative of sullyassembled cells, and data referenced above for the embodiments refers tothe positive electrode only. In certain embodiments, better performanceis provided than lithium ion batteries with an inverse opal structureand a Ni(OH)₂ psuedocapacitor with a foam type microstructure operatingat a much wider potential window (2V and 1.8V respectively).

FIG. 8 depicts Ragone plots. Section 805 of FIG. 8 depicts gravimetricpower densities of Ni/Hi(OH)₂ electrode in comparison to variouselectrode, full batteries and supercapictors. Section 810 of FIG. 8depicts volumetric power densities of Ni/Hi(OH)₂ electrode in comparisonto various electrode, full batteries and supercapictors.

FIG. 9 depicts a graphical representation of a battery including acomposite electrode according to one or more embodiments. According toone embodiment, a battery 900 includes an anode electrode 905, cathode910, electrolyte 915 and electrochemical cell 920. Battery 900 mayrelate to a nickel metal hydride battery. According to anotherembodiment, cathode electrode 910 is a composite electrode having aporous structure. In one embodiment, cathode electrode 910 is acomposite electrode formed by a metal structure having a uniform porestructure with a defined internal surface area per unit volume and anactive material coating the metal structure. In one embodiment,thickness of the active material of cathode electrode 910 is controlledto tune the electrochemical performance of the composite electrode.

The cathode electrode 910 may include a metal structure is formed bynickel. The pore geometry and distribution of the metal structure istuned for electrochemical performance of the composite electrode.According to another embodiment, the active material coating isNickel/Nickel hydroxide (Ni/Ni(OH)₂) for cathode electrode 910. Thethickness of the composite electrode of cathode 910 is within the rangeof about 15 μm to about 500 μm.

Battery 900 may relate to a nickel metal hydride battery, nickel airbattery and batteries in general.

FIG. 10 depicts a process for creating a composite electrode accordingto one or more embodiments. According to one embodiment, process 1000employs a polymer template. The polymer template (e.g., polymer template505) may be formed from a bicontinuous interfacially jammed emulsiongels (e.g., bijels). According to another embodiment, the polymertemplate (e.g., polymer template 505) of process 1000 includes a uniformpore geometry and pore distribution.

In one embodiment, process 1000 is initiated by depositing metal (e.g.,nickel, etc.) on a polymer template at block 1005. According to anotherembodiment, process may be initiated by generating a polymer template atoptional block 1006 prior to depositing metal on the template at block1005.

Process 1000 may include forming the polymer template with a desiredpore structure prior to depositing the layer of metal material on thepolymer template at block 1005. Block 1006 may include generating apolymer template by arrested phase separation of a binary liquid mixture(e.g., mixture 305) undergoing spinodal decomposition in the presence ofneutrally wetting colloidal particles (e.g., particles 310). The polymertemplate may be formed at optional block 1006 to include a uniform poregeometry with a uniform pore distribution. In one embodiment, polymertemplate generation at optional block 1006 includes spinodaldecomposition from one thermodynamic phase to form two coexistingphases. According to another embodiment, the spinodal decomposition iscontrolled to provide morphologies relevant to electrochemicalapplications.

The polymer template formed at optional block 1006, and/or employed inblock 1005, may include a pore morphology that may be similar to asponge. Unlike sponges which typically have pockets or voids that arerandomly distributed and sometimes isolated from one another, thepolymer template of process 1000 can include a uniform channel size thatis continuous throughout the morphology. The pore morphology of thepolymer template can allow for the internal channel size to becontrolled, and process 1000 may produce this continuity through aspinodal processing of a bijel. In one embodiment, channel size can betuned within a range between 5 μm to 550 μm. According to one exemplaryembodiment, a channel size of 150 μm is typically the upper range for acomposite electrode application. Channel size may be controlled byparticles jammed at interfaces (e.g., see FIG. 3). The point at whichparticles jam can dictate the size of the channels. In one embodiment,optional block 1006 includes application of a temperature change to agel like emulsion to create a gel with the unique microstructure.

At block 1005, process 1000 includes depositing a layer of metalmaterial on a polymer template to form a metal coated structure. In oneembodiment, the polymer template is a porous structure having a uniformpore structure with a defined internal surface area per unit volume.According to another embodiment, prior to coating and in associationwith coating at block 1005, silica particles may be removed from thepolymer template by etching such that the template includes a polymerphase and voids. At block 1005, metal, such as nickel, is deposited onthe internal surfaces of the template.

At block 1010, process 1000 includes removing polymer material from themetal coated structure to form a metal shell (e.g., metal shell 515,etc.). In one embodiment, the polymer is removed by sintering the metalcoated structure to form the metal shell. For example, the coatedtemplate is put in a furnace to burn out the polymer material andscinter particles on the surface to form a hollow and very light weighthigh surface area. In certain embodiments, block 1010 may also includeperforming a reduction process on the metal shell. In one embodiment,the metal shell includes a uniform pore structure within the metal shellwith an internal surface area per unit volume based on the polymertemplate. In one embodiment, pores of the metal shell are uniform andrange from about 5 μm to about 450 μm in length. According to anotherembodiment, the metal shell is a nickel shell.

At block 1015, process 1000 includes depositing an active material onthe metal shell to form a composite electrode (e.g., composite electrode525, etc.). In one embodiment, thickness of the active material in thecomposite electrode is controlled to tune the electrochemicalperformance of the composite electrode. In one embodiment, activematerial is Nickel/Nickel Hydroxide (Ni/Ni(OH)₂). In one embodiment, thethickness of the active material is about 1 μm thick. Performance of thecomposite electrode is based on the internal surface area per unitvolume and thickness of the active material deposited at block 1015.According to another embodiment, electrochemical performance of thecomposite electrode is governed by independent tuning of pore diameterand thickness of the active material deposited at block 1015. Block 1015results in formation of a composite electrode which may be configured asa porous current collector in a battery (e.g., battery 900). In oneembodiment, the composite electrode created by process 1000 isconfigured as a cathode for a nickel metal hydride battery. According toanother embodiment, thickness of the composite electrode is within therange of about 15 μm to about 500 μm.

According to another embodiment, process 1000 may be directed to variouschemistries beyond Nickel/Nickel Hydroxide chemistries.

While this disclosure has been particularly shown and described withreferences to exemplary embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the claimed embodiments

However, the subject technology is not limited to the specific detailsset forth herein and may be practiced without these specific details. Insome instances, structures and components are shown in block diagramform in order to avoid obscuring the concepts of the subject technology.

What is claimed is:
 1. A nickel battery electrode comprising: acomposite electrode having a porous structure, the composite electrodeformed by a metal structure having a uniform pore structure with adefined internal surface area per unit volume, wherein the uniform porestructure of the metal structure is formed using a bicontinuousinterfacially jammed emulsion gel template, wherein the uniform porestructure includes an internal surface area per unit volume based on thepolymer template and wherein the uniform pore structure has a uniformchannel size continuous throughout a pore morphology and a uniform poredistribution, and an active material coating the metal structure,wherein the active material has a thickness, and wherein the thicknessof the active material in the composite electrode and internal surfacearea per unit volume of the pore structure control electrochemicalperformance of the composite electrode.
 2. The nickel battery electrodeof claim 1, wherein the metal structure is formed by nickel.
 3. Thenickel battery electrode of claim 1, wherein a pore geometry anddistribution of the metal structure controls electrochemical performanceof the composite electrode, and wherein channel size of the uniform porestructure is controlled by particles jammed at interfaces of thebicontinuous interfacially jammed emulsion gel template.
 4. The nickelbattery electrode of claim 1, wherein the active material coating isNickel/Nickel Hydroxide (Ni/Ni(OH)₂) having a thickness of about 1 μm.5. The nickel battery electrode of claim 1, wherein thickness of thecomposite electrode is within the range of about 15 μm to about 500 μm.6. A battery comprising: an electrolyte; an anode electrode; and ancathode electrode, wherein the cathode is a composite electrode having aporous structure, the composite electrode formed by a metal structurehaving a uniform pore structure with a defined internal surface area perunit volume, wherein the uniform pore structure of the metal structureis formed using a bicontinuous interfacially jammed emulsion geltemplate, wherein the uniform pore structure includes an internalsurface area per unit volume based on the polymer template and whereinthe uniform pore structure has a uniform channel size continuousthroughout a pore morphology and a uniform pore distribution, and anactive material coating the metal structure, wherein the active materialhas a thickness, and wherein the thickness of the active material in thecomposite electrode-and internal surface area per unit volume of thepore structure controls electrochemical performance of the compositeelectrode.
 7. The battery of claim 6, wherein the metal structure isformed by nickel.
 8. The battery of claim 6, wherein a pore geometry anddistribution of the metal structure controls electrochemical performanceof the composite electrode, and wherein channel size of the uniform porestructure is controlled by particles jammed at interfaces of thebicontinuous interfacially jammed emulsion gel template.
 9. The batteryof claim 6, wherein the active material coating is Nickel/NickelHydroxide (Ni/Ni(OH)₂) having a thickness of about.
 10. The battery ofclaim 6, wherein thickness of the composite electrode is within therange of about 15 μm to about 500 μm.